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<div class="titlepage"><div><div><h5 class="title">
<a name="boost_asio.reference.ip__basic_resolver.async_resolve.overload1"></a><a class="link" href="overload1.html" title="ip::basic_resolver::async_resolve (1 of 5 overloads)">ip::basic_resolver::async_resolve
          (1 of 5 overloads)</a>
</h5></div></div></div>
<p>
            Asynchronously perform forward resolution of a query to a list of entries.
          </p>
<pre class="programlisting"><span class="keyword">template</span><span class="special">&lt;</span>
    <span class="keyword">typename</span> <a class="link" href="../../ResolveToken.html" title="Resolve token requirements">ResolveToken</a> <span class="special">=</span> <span class="identifier">default_completion_token_t</span><span class="special">&lt;</span><span class="identifier">executor_type</span><span class="special">&gt;&gt;</span>
<a class="link" href="../../asynchronous_operations.html#boost_asio.reference.asynchronous_operations.automatic_deduction_of_initiating_function_return_type"><span class="emphasis"><em>DEDUCED</em></span></a> <span class="identifier">async_resolve</span><span class="special">(</span>
    <span class="identifier">string_view</span> <span class="identifier">host</span><span class="special">,</span>
    <span class="identifier">string_view</span> <span class="identifier">service</span><span class="special">,</span>
    <span class="identifier">ResolveToken</span> <span class="special">&amp;&amp;</span> <span class="identifier">token</span> <span class="special">=</span> <span class="identifier">default_completion_token_t</span><span class="special">&lt;</span> <span class="identifier">executor_type</span> <span class="special">&gt;());</span>
</pre>
<p>
            This function is used to resolve host and service names into a list of
            endpoint entries.
          </p>
<h6>
<a name="boost_asio.reference.ip__basic_resolver.async_resolve.overload1.h0"></a>
            <span class="phrase"><a name="boost_asio.reference.ip__basic_resolver.async_resolve.overload1.parameters"></a></span><a class="link" href="overload1.html#boost_asio.reference.ip__basic_resolver.async_resolve.overload1.parameters">Parameters</a>
          </h6>
<div class="variablelist">
<p class="title"><b></b></p>
<dl class="variablelist">
<dt><span class="term">host</span></dt>
<dd><p>
                  A string identifying a location. May be a descriptive name or a
                  numeric address string. If an empty string and the passive flag
                  has been specified, the resolved endpoints are suitable for local
                  service binding. If an empty string and passive is not specified,
                  the resolved endpoints will use the loopback address.
                </p></dd>
<dt><span class="term">service</span></dt>
<dd><p>
                  A string identifying the requested service. This may be a descriptive
                  name or a numeric string corresponding to a port number. May be
                  an empty string, in which case all resolved endpoints will have
                  a port number of 0.
                </p></dd>
<dt><span class="term">token</span></dt>
<dd>
<p>
                  The <a class="link" href="../../../overview/model/completion_tokens.html" title="Completion Tokens">completion
                  token</a> that will be used to produce a completion handler,
                  which will be called when the resolve completes. Potential completion
                  tokens include <a class="link" href="../../use_future.html" title="use_future"><code class="computeroutput"><span class="identifier">use_future</span></code></a>, <a class="link" href="../../use_awaitable.html" title="use_awaitable"><code class="computeroutput"><span class="identifier">use_awaitable</span></code></a>, <a class="link" href="../../yield_context.html" title="yield_context"><code class="computeroutput"><span class="identifier">yield_context</span></code></a>, or a function
                  object with the correct completion signature. The function signature
                  of the completion handler must be:
                </p>
<pre class="programlisting"><span class="keyword">void</span> <span class="identifier">handler</span><span class="special">(</span>
  <span class="keyword">const</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">system</span><span class="special">::</span><span class="identifier">error_code</span><span class="special">&amp;</span> <span class="identifier">error</span><span class="special">,</span> <span class="comment">// Result of operation.</span>
  <span class="identifier">resolver</span><span class="special">::</span><span class="identifier">results_type</span> <span class="identifier">results</span> <span class="comment">// Resolved endpoints as a range.</span>
<span class="special">);</span>
</pre>
<p>
                  Regardless of whether the asynchronous operation completes immediately
                  or not, the completion handler will not be invoked from within
                  this function. On immediate completion, invocation of the handler
                  will be performed in a manner equivalent to using <a class="link" href="../../async_immediate.html" title="async_immediate"><code class="computeroutput"><span class="identifier">async_immediate</span></code></a>.
                </p>
</dd>
</dl>
</div>
<p>
            A successful resolve operation is guaranteed to pass a non-empty range
            to the handler.
          </p>
<h6>
<a name="boost_asio.reference.ip__basic_resolver.async_resolve.overload1.h1"></a>
            <span class="phrase"><a name="boost_asio.reference.ip__basic_resolver.async_resolve.overload1.completion_signature"></a></span><a class="link" href="overload1.html#boost_asio.reference.ip__basic_resolver.async_resolve.overload1.completion_signature">Completion
            Signature</a>
          </h6>
<pre class="programlisting"><span class="keyword">void</span><span class="special">(</span><span class="identifier">boost</span><span class="special">::</span><span class="identifier">system</span><span class="special">::</span><span class="identifier">error_code</span><span class="special">,</span> <span class="identifier">results_type</span><span class="special">)</span>
</pre>
<h6>
<a name="boost_asio.reference.ip__basic_resolver.async_resolve.overload1.h2"></a>
            <span class="phrase"><a name="boost_asio.reference.ip__basic_resolver.async_resolve.overload1.remarks"></a></span><a class="link" href="overload1.html#boost_asio.reference.ip__basic_resolver.async_resolve.overload1.remarks">Remarks</a>
          </h6>
<p>
            On POSIX systems, host names may be locally defined in the file <code class="computeroutput"><span class="special">/</span><span class="identifier">etc</span><span class="special">/</span><span class="identifier">hosts</span></code>.
            On Windows, host names may be defined in the file <code class="computeroutput"><span class="identifier">c</span><span class="special">:\</span><span class="identifier">windows</span><span class="special">\</span><span class="identifier">system32</span><span class="special">\</span><span class="identifier">drivers</span><span class="special">\</span><span class="identifier">etc</span><span class="special">\</span><span class="identifier">hosts</span></code>.
            Remote host name resolution is performed using DNS. Operating systems
            may use additional locations when resolving host names (such as NETBIOS
            names on Windows).
          </p>
<p>
            On POSIX systems, service names are typically defined in the file <code class="computeroutput"><span class="special">/</span><span class="identifier">etc</span><span class="special">/</span><span class="identifier">services</span></code>.
            On Windows, service names may be found in the file <code class="computeroutput"><span class="identifier">c</span><span class="special">:\</span><span class="identifier">windows</span><span class="special">\</span><span class="identifier">system32</span><span class="special">\</span><span class="identifier">drivers</span><span class="special">\</span><span class="identifier">etc</span><span class="special">\</span><span class="identifier">services</span></code>.
            Operating systems may use additional locations when resolving service
            names.
          </p>
</div>
<div class="copyright-footer">Copyright © 2003-2025 Christopher M.
      Kohlhoff<p>
        Distributed under the Boost Software License, Version 1.0. (See accompanying
        file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
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